Fig. 1.

Compositional depth profiles of the CIS/GaAs samples subject to different treatments. a ²³Na SIMS profiles (left axis) and absolute Na concentration from APT (right axis, only for Se+Na₂Se sample) expressed as a function of depth from the CIS surface (note the different film thickness); b corresponding Ga depth gradient expressed as ⁶⁹Ga/(¹¹⁵In + ⁶⁹Ga) SIMS signal ratio as a function of distance from the CIS/GaAs interface. c Extent of Na in-diffusion in the CIS films from the surface until the GaAs interface expressed as integrated ²³Na SIMS counts (green bars). Corresponding integrated ⁶⁹Ga/(¹¹⁵In + ⁶⁹Ga) SIMS signal ratios divided by the film thickness (red bars). Extent of In out-diffusion from the films into the GaAs substrate expressed as ¹¹⁵In/(¹¹⁵In + ⁶⁹Ga) integrated SIMS signal ratio until 500 nm deep in the substrate from the interface (blue bars). The black circles and numbers are the GGI ratios measured by SEM-EDS with an acceleration voltage of 7 kV (corresponding to more than 90% of In/Ga L X-rays arising from first 200 nm depth according to Casino Monte Carlo simulations³⁹). d GGI depth profiles estimated by correcting the SIMS profiles in b by the natural isotopic abundances of In (95.71%) and Ga (60.11%) (solid lines), by nano-AES cross sectional analysis (dashed lines) and APT (dotted lines, the depth range is limited by the sample preparation)